Nothing wrong with this idea, but be aware of the following:
1) Cables drift with wind - there is the possibility that the launch cable could drift across to the powered side, especially if a student / early solo is struggling with the take-offs (you don't say whether the site is winch launch, aerotow or both so I'm thinking worst case scenario here).
2) There may be a local soaring instruction that you don't know about, allowing the gliders to thermal once they're on the powered side, so long as they're above powered circuit height (Have flown somewhere were this was the case). In this case you're going to meet people intent on getting height fairly soon after launch so that they can disappear on cross country tasks / further climb. This won't have a happy outcome
So - how about a slight modification to your idea. Approach the airfield as you've stated, remaining on the powered side. You know the runway direction, so you can work out roughly how that will lie on the field. Identify the
airfield from a distance - turn left and descend to circuit height rolling out on a track similar to the runway heading. You won't have identified the runway at this point, but that's not a problem. You will have avoided any gliders operating in scenario (2) above and any cables from scenario (1).
On reaching circuit height - Right turn of 180 degrees to bring you onto a downwind heading at the start of or preferably before the downwind leg. Fly downwind - identify runway, inspect surface and situation, continue with circuit as normal.